The present invention generally relates to a system and a method for providing an antenna and, more specifically, to a system and a method for providing a quasi-isotropic antenna.
In an increasingly mobile working environment, short-range communications standards were developed to help in eliminating wires and cables between stationary devices, mobile devices and combinations thereof. Examples of short-range communications standards include, for example, IEEE 802.11 and HyperLan. Another example of a short-range communications standard is the global standard called Bluetooth. Bluetooth is a relatively short-ranged wireless technology that has found application in ranges under approximately 100 yards and has proven popular in providing personal area networks (PANs) located in homes and small offices. Unlike other conventional wireless techniques such as infrared (e.g., IrDA), Bluetooth does not require a direct line of sight for communications. In addition, Bluetooth can provide, for example, point-to-point and/or point-to-multipoint connections in piconet and scatternet configurations.
Bluetooth generally includes hardware components, software and interoperability requirements. Bluetooth hardware includes a 2.4 GHz Bluetooth radio and provides spread spectrum techniques such as frequency hopping. For example, Bluetooth may operate in a 2.4 GHz to 2.48 GHz range in which signal hops may occur among 79 frequencies at 1 MHz intervals. Furthermore, at present, Bluetooth can support voice channels, for example, of 64 kb/s and asynchronous data channels of, for example, 723.2 kb/s asymmetric or 433.9 kb/s symmetric.
In theory, Bluetooth technology can be installed in handheld wireless communications devices such as, for example, cellular phones or personal digital assistants (PDAs). For example, a Bluetooth antenna can be mounted on a handheld device in addition to the cellular antenna. However, in general, Bluetooth technology tends to interfere with the cellular transceivers including cellular antennas. Furthermore, the converse is true that cellular transceivers including cellular antennas tend to interfere with Bluetooth technology. Accordingly, neither the Bluetooth antenna nor the cellular antenna works effectively.
In another conventional device, a Bluetooth patch antenna is placed on the back of the cellular phone with additional shielding between the Bluetooth antenna and the back of the cellular phone. However, such a device performs poorly if, for example, the cellular phone is disposed on its back while lying on a table. In this position, the shielding and the table block effective communications with the Bluetooth antenna.
The consequences become exacerbated in situations in which the Bluetooth technology is used for automated communications. For example, the Bluetooth technology may be configured to transfer e-mail messages from a local wireless network in an office to a handheld device carried by the user when the user is in Bluetooth range (e.g., in the office) of the local wireless network. If the user places the handheld device in such an orientation as to effectively shield the Bluetooth antenna from the local wireless network (despite being in range of the local wireless network), then the e-mail messages will not be transferred to the handheld device, the user will be unaware of communications problems and the user will assume that he or she had no unread e-mail messages on the local wireless network.
The short-range wireless antennas in known wireless communications devices do not perform well. Specifically, the known wireless antennas have anisotropic radiation patterns. This results in failed short-range wireless communications when the wireless communication device is orientated in certain positions. There exists a need to provide a short-range wireless antenna in a wireless communications device in which the short-range wireless antenna has quasi-isotropic radiation characteristics.
Briefly, the present invention uses a microstrip, line or trace forming part of the wireless communications device""s electrical circuitry to function as a short-range wireless antenna. The microstrip, line or trace is structured to transmit and receive short-range communications signals. The structure of the microstrip, line or trace includes many branches that meander in a plurality of directions to provide the antenna with quasi-isotropic radiation characteristics.
Advantages of the present invention include forming a short-range wireless antenna in a wireless communications device by using an existing microstrip, line or trace. The present invention also has an advantage in that existing shielding may provide isolation between the existing antenna and the microstrip, line or trace that has been adapted to be a short-range antenna. Therefore, a separate short-range antenna and additional shielding is not needed which results in cost reduction and space savings in an already crowded circuit board of the wireless communications device.
An additional advantage is that the meandering line shape of the microstrip, line or trace provides an antenna with quasi-isotropic radiation characteristics. Such quasi-isotropic radiation characteristics are further enhanced in configurations in which the microstrip, line or trace is disposed on the front side and the rear side of a printed circuit board of the wireless communications device, or meanders away from the board in a vertical direction. Furthermore, the microstrip, line or trace may operate as a specific absorption rate element that redirects radiation away from the back of the wireless device and the user.
These and other features and advantages of the present invention will be appreciated by reviewing the following detailed description of the present invention and the accompanying figures.